Problem with structure field hints

[Zerg17]

Environment

• OS and Version: Windows 10 LTSC 2018
• VS Code Version: 1.129.1
• C/C++ Extension Version: 1.32.2

Bug Summary and Steps to Reproduce

1. Create a main.c file with the following contents::

struct {
    int a;
    int b;
} test;

int main(){
    int err = 0;

    test.
    err++;

    test.
    err = err + 1;

    test.
    err--;
}

It's expected that pressing ctrl+space will give us a tooltip, but the first and third "test." the hint doesn't appear, it only works for the second one. ++, --, +=, -=, *=, /=, |=, &=, and ^=/ have similar behavior.

Configuration and Logs

loggingLevel: 6
loggingLevel был изменен на: Debug
Обработан файл c_cpp_properties.json за 0.0065977 с
Intellisense update pending for: file:///c%3A/prog/c/bugTest/main.c
Завершение работы сервера IntelliSense: C:\prog\c\bugTest\main.c
LSP: (received) cpptools/didChangeCppProperties (id: 453)
LSP: (invoked) cpptools/didChangeCppProperties (id: 453)
Попытка получить значения по умолчанию из компилятора C++ в свойстве "compilerPath": "cl.exe"
Попытка получить значения по умолчанию из компилятора C в свойстве "compilerPath": "cl.exe"
  Папка C:\PROGRAM FILES (X86)\MICROSOFT VISUAL STUDIO\18\BUILDTOOLS\VC\TOOLS\MSVC\14.50.35717\INCLUDE будет индексироваться
  Папка C:\PROG\C\BUGTEST будет индексироваться
LSP: Sending response (id: 453)
LSP: (received) cpptools/getFoldingRanges: file:///c%3A/prog/c/bugTest/main.c (id: 454)
LSP: (invoked) cpptools/getFoldingRanges: file:///c%3A/prog/c/bugTest/main.c (id: 454)
LSP: Sending response (id: 454)
LSP: (received) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 455)
LSP: (invoked) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 455)
LSP: Sending response (id: 455)
LSP: $/cancelRequest (<unknown/completed>, id: 455)
LSP: (received) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 456)
LSP: (invoked) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 456)
LSP: Sending response (id: 456)
IntelliSense update scheduled and TU acquisition started for: file:///c%3A/prog/c/bugTest/main.c
Populating file name cache...
Done populating filename cache. Elapsed time: 0 ms
Expanding recursive includes for: C:\PROG\C\BUGTEST\MAIN.C
Done expanding recursive includes for: C:\PROG\C\BUGTEST\MAIN.C
Reducing recursive includes for: C:\PROG\C\BUGTEST\MAIN.C
Done reducing recursive includes for: C:\PROG\C\BUGTEST\MAIN.C
Отправка аргументов компиляции для C:\prog\c\bugTest\main.c.
  system include: C:\PROGRAM FILES (X86)\MICROSOFT VISUAL STUDIO\18\BUILDTOOLS\VC\TOOLS\MSVC\14.50.35717\INCLUDE
  define: _DEBUG
  define: UNICODE
  define: _UNICODE
  stdver: ms_c17
  intelliSenseMode: windows-msvc-x64
Время обновления IntelliSense (в секундах): 0.038
LSP: (received) cpptools/getFoldingRanges: file:///c%3A/prog/c/bugTest/main.c (id: 457)
LSP: (invoked) cpptools/getFoldingRanges: file:///c%3A/prog/c/bugTest/main.c (id: 457)
LSP: Sending response (id: 457)
LSP: (received) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 458)
LSP: (invoked) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 458)
LSP: Sending response (id: 458)
LSP: (received) cpptools/getFoldingRanges: file:///c%3A/prog/c/bugTest/main.c (id: 459)
LSP: (invoked) cpptools/getFoldingRanges: file:///c%3A/prog/c/bugTest/main.c (id: 459)
LSP: Sending response (id: 459)
LSP: (received) cpptools/didChangeActiveEditor: file:///c%3A/prog/c/bugTest/main.c
LSP: (invoked) cpptools/didChangeActiveEditor: file:///c%3A/prog/c/bugTest/main.c
LSP: (received) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 460)
LSP: (invoked) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 460)
LSP: Sending response (id: 460)
LSP: (received) cpptools/didChangeVisibleTextEditors
LSP: (invoked) cpptools/didChangeVisibleTextEditors
LSP: (received) cpptools/didChangeVisibleTextEditors
LSP: (invoked) cpptools/didChangeVisibleTextEditors
LSP: (received) cpptools/didChangeTextEditorSelection
LSP: (invoked) cpptools/didChangeTextEditorSelection
LSP: (received) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 461)
LSP: (invoked) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 461)
LSP: Sending response (id: 461)
LSP: (received) textDocument/completion: file:///c%3A/prog/c/bugTest/main.c (id: 462)
LSP: (invoked) textDocument/completion: file:///c%3A/prog/c/bugTest/main.c (id: 462)
auto_complete::handle_completion: file:///c%3A/prog/c/bugTest/main.c (9:10)
Предлагается завершение.
LSP: Sending response (id: 462)
LSP: (received) cpptools/didChangeTextEditorSelection
LSP: (invoked) cpptools/didChangeTextEditorSelection
LSP: (received) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 463)
LSP: (invoked) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 463)
LSP: Sending response (id: 463)
LSP: (received) textDocument/completion: file:///c%3A/prog/c/bugTest/main.c (id: 464)
LSP: (invoked) textDocument/completion: file:///c%3A/prog/c/bugTest/main.c (id: 464)
auto_complete::handle_completion: file:///c%3A/prog/c/bugTest/main.c (12:10)
Предлагается завершение.
LSP: Sending response (id: 464)
LSP: (received) completionItem/resolve (id: 465)
LSP: (invoked) completionItem/resolve (id: 465)
LSP: Sending response (id: 465)
LSP: (received) cpptools/didChangeTextEditorSelection
LSP: (invoked) cpptools/didChangeTextEditorSelection
LSP: (received) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 466)
LSP: (invoked) cpptools/getCodeActions: file:///c%3A/prog/c/bugTest/main.c (id: 466)
LSP: Sending response (id: 466)
LSP: (received) textDocument/completion: file:///c%3A/prog/c/bugTest/main.c (id: 467)
LSP: (invoked) textDocument/completion: file:///c%3A/prog/c/bugTest/main.c (id: 467)
auto_complete::handle_completion: file:///c%3A/prog/c/bugTest/main.c (15:10)
Предлагается завершение.
LSP: Sending response (id: 467)

Other Extensions

No response

Additional context

No response

[Zerg17]

[sean-mcmanus]

@Zerg17 Findings...

1. Repros for C and not C++.
2. Also repros in VS 2026 (shared IntelliSense completion code).
3. It stops reproing if ; is added to the right of the ..
4. It doesn't repro when undefinedSymbol++; is used instead of err++.
5. It also repro if the newline is replace by a space.
6. It doesn't repro with ++err.

I vaguely remember this may have been reported previously.

[Zerg17]

The problem disappears not only when adding ;, but also any character with which the name of a structure field can begin.

The behavior with the pointer is similar.

The behavior with undefinedSymbol is similar.

typedef struct {
    int a;
    int b;
} test_t;

int main(){
    test_t test;
    test_t* test_ptr = &test;

    test_ptr->
    undefinedSymbol++;

    test_ptr->
    undefinedSymbol = undefinedSymbol + 1;

    test_ptr->
    undefinedSymbol--;
}